(a) Field of the Invention
The present invention relates to a scanning apparatus for use in a cross-sectional inspection unit, and more particularly it relates to scanning apparatus of the type described above arranged so as to be operative that a required cross section of an object to be inspected is scanned in various different directions by X-ray, and that the absorption information of X-ray obtained during the scanning is inputted in a computer, and that the cross-sectional image obtained as the result of computation is displayed on a surface such as a Braun tube.
(b) Description of the Prior Art
A scanning apparatus arranged so that a rotatable disc supporting an X-ray source and a detector is subjected to only rotational movement is known. In such known scanning apparatus, the rotatable disc is required to be rotated at a constant speed through the measurement interval which corresponds to the period of time in which X-ray emission continues and in which X-ray having passed through the object to be inspected is being received by the detector. In the past, it has been the usual way of accomplishing this requirement by preliminarily subjecting the rotatable disc to rotation before the starting of inspection by X-ray, and, at the end of inspection, by subjecting the rotating disc to gradual braking. In view of the fact, however, that the rotatable disc of this type has a very great weight of its own, and in view of the requirement that this disc carries thereon an X-ray source and a detector or other equipment which have to be kept from impact, the pre-inspection rotation period and the braking period tend to be quite lengthy.
On the other hand, an inspection of the object by X-ray requires that the rotatable disc be rotated through a substantial distance or angle or time. This, in turn, makes difficult the handling of the cable which extends from various kinds of equipment mounted on the rotatable disc and is led out to the outside of the scanning apparatus. In order to meet this requirement, it has been proposed in the past that the cable is given a substantial length of play so that the cable may be allowed to be fed out freely progressively as the disc rotates. This, however, still involves the risks that the cable could be bent forcibly or otherwise damaged during its feed and rewinding. Another known proposal is that the cable is adapted to be wound around a bobbin which is provided on the rotatable disc. This known arrangement still is entrained by a risk that the constant movement of the disc is hampered during the rewinding of the cable around the bobbin.